1. T cells in the immune system can be categorized into different types. What type of T cell directly kills infected body cells?

A. Helper T cells
B. Cytotoxic T cells
C. Regulatory T cells
D. Memory T cells

Correct answer: B

Rationale: Cytotoxic T cells directly kill infected body cells. These T cells recognize and destroy cells that are infected with viruses or other pathogens. They are crucial for eliminating threats within the body. Helper T cells, on the other hand, assist in coordinating the immune response by activating other immune cells. Regulatory T cells help maintain immune tolerance and prevent autoimmune reactions. Memory T cells are responsible for 'remembering' specific pathogens to mount a faster and stronger immune response upon re-exposure. Therefore, cytotoxic T cells are the correct answer as they directly target and kill infected cells.

2. Which nitrogenous bases pair with each other in DNA?

A. A-G and T-C
B. A-T and C-G
C. -A and T-T
D. C-C and G-G

Correct answer: B

Rationale: Rationale: In DNA, nitrogenous bases pair with each other in a specific manner known as complementary base pairing. Adenine (A) always pairs with Thymine (T), and Cytosine (C) always pairs with Guanine (G). This pairing is essential for maintaining the structure and function of DNA. Therefore, option B is the correct answer as it correctly identifies the nitrogenous bases that pair with each other in DNA.

3. Pinpoint the smallest bone in the human body.

A. Stapes (Middle ear bone)
B. Patella (Kneecap)
C. Phalanges (Finger bones)
D. Ribs

Correct answer: A

Rationale: The stapes, crucial for hearing, transmits and amplifies sound vibrations. Despite its size, it plays a vital role in auditory perception.

4. What is the term for an organism with two different alleles for a gene?

A. Homozygous
B. Heterozygous
C. Dominant
D. Recessive

Correct answer: B

Rationale: An organism with two different alleles for a gene has a mixed genotype and may exhibit either the dominant or recessive trait depending on the specific gene and its alleles.

5. Which of the following is NOT a risk factor for developing atherosclerosis?

A. High blood pressure
B. High levels of LDL cholesterol
C. Regular physical activity
D. Smoking

Correct answer: C

Rationale: Regular physical activity is NOT a risk factor for developing atherosclerosis. In fact, engaging in regular physical activity can help reduce the risk of developing atherosclerosis by improving cardiovascular health, lowering blood pressure, and reducing LDL cholesterol levels. High blood pressure, high levels of LDL cholesterol, and smoking are all known risk factors for atherosclerosis. High blood pressure can damage blood vessels, making them more susceptible to plaque buildup. High levels of LDL cholesterol can lead to the accumulation of plaque in the arteries, narrowing the passageways and increasing the risk of atherosclerosis. Smoking is harmful to blood vessels, promoting inflammation and the formation of plaque. Therefore, regular physical activity is actually a protective factor against atherosclerosis rather than a risk factor.

6. A baseball is thrown into the air. At the peak of its trajectory, which of the following forces is acting on the ball?

A. Only gravitational force
B. Only the force of air resistance
C. Both gravitational force and the force of air resistance
D. Neither gravitational force nor the force of air resistance

Correct answer: A

Rationale: At the peak, the ball momentarily stops moving upwards. Its inertia keeps it moving horizontally, but there is no force propelling it upwards except for gravity pulling it down.